zfs cannot unmount (cannot unshare)

I have installed Solaris 11 Express on my machine, created a raidz2 zpool named shares and set up sharing (zfs set sharesmb=on shares). I also created a script for automatic backuping using snapshots.

Everything worked fine. But yesterday I tried recovering from one of those backuped snapshots:

zpool destroy shares
zpool create raidz2 shares ... 
zfs unmount shares
zfs send backup/shares@... | zfs receive -F shares
zfs mount shares
sharemgr start -P smb zfs

The restoration seems to have succeeded, even sharing works. But now I cannot unmount the shares filesystem.

zfs unmount shares

yields this output: cannot unshare 'shares': not found: unshare(1M) failed

I tried to play with unshare for a while but did not succeed.

Thanks for your help,
Dusan

Can you try with Solaris 11 pre-release Beta versions?
Solaris 11 Express is not in use now, I guess.
Codes have been stabled from Solaris 11 builds 160 onwards.